30 NERVES AND MUSCLES 



without the nerves ; they are essential to all vital 

 motions. Under their influence, the viscera produce 

 those compounds, which, while they protect the orga- 

 nism from the action of the oxygen of the atmo- 

 sphere, give rise to animal heat ; and when the 

 nerves cease to perform their functions, the whole 

 process of the action of oxygen must assume another 

 form. When the pons Varolii is cut through in the 

 dog, or when a stunning blow is inflicted on the 

 back of the head, the animal continues to respire for 

 some time, often more rapidly than in the normal 

 state; the frequency of the pulse at first rather 

 increases than diminishes, yet the animal cools as 

 rapidly as if sudden death had occurred. Exactly 

 similar observations have been made on the cutting 

 of the spinal cord, and of the par vagum. The 

 respiratory motions continue for a time, but the 

 oxygen does not meet with those substances with 

 which, in the normal state, it would have combined ; 

 because the paralyzed viscera will no longer furnish 

 them. The singular idea that the nerves produce 

 animal heat, has obviously arisen from the notion 

 that the inspired oxygen combines with carbon, in 

 the blood itself; in which case the temperature of 

 the body, in the above experiments, certainly, ought 

 not to have sunk. But, as we shall afterwards see, 

 there cannot be a more erroneous conception than 

 this. 



As by the division of the pneumogastric nerves 

 the motion of the stomach and the secretion of the 



